The present invention pertains to machines for applying coatings and, more particularly, to a machine for applying coatings to stringers.
Stringers are generally straight, long, narrow components of the structural skeleton of an aircraft. The stringers are mounted to the interior surface of the skin of the aircraft to reinforce the skin. Whereas some stringers are uniform along their length, other stringers include irregular portions, which are referred to as joggles. The joggles allow the stringers to match irregularities of the skin surface and further allow the stringers to extend over straps that are attached to the skin and extend perpendicular to the stringers.
It is common to apply a coating material, such as a polysulfide sealant, to the surface of a stringer that abuts the skin of the aircraft. The coating protects the aircraft from corrosion. The coating is applied to the stringer prior to mounting the stringer to the skin. As one example, the coating is conventionally initially applied with a pneumatic applicator assembly that is manually moved generally along the length of the stringer. Compressed air is supplied to a chamber of the applicator assembly to force the coating material from a reservoir of the applicator assembly. The coating material is discharged from the reservoir through a nozzle that directs the coating material onto the stringer, so that a long bead of the coating material extends along the length of the stringer. Thereafter, an applicator roller is manually rolled along the length of the stringer to spread the coating material.
Manually applying coatings to the many stringers of an aircraft is very labor intensive. It is desirable to reduce the cost of manufacturing aircraft by reducing labor costs; therefore, manually applying the coating material to stringers is disadvantageous. Further, special care must be taken when manually applying the coating material to ensure that the coating material is well applied, especially in the vicinity of joggles. Depending upon the skill of the operator applying the coating, some of the stringers, or at least the joggles thereof, may not be adequately coated in some situations, which can disadvantageously result in premature corrosion of the aircraft incorporating the stringers.
The present invention solves the above and other problems by providing a coating machine that automatically applies coatings to the surfaces of stringers. The applied coatings are generally consistent from stringer to stringer and are generally uniform along the length of each stringer, even if the stringers have joggles or different overall dimensions.
In accordance with one aspect of the present invention, a stringer is introduced into an upstream end of the coating machine, and thereafter the stringer is drawn into the coating machine. As the stringer passes through the coating machine, a coating is applied to the surface of stringer that is to abut the skin of an aircraft. Thereafter, the stringer is discharged from the downstream end of the coating machine.
In accordance with another aspect of the present invention, the coating machine includes a conveyor having a conveyor surface that extends in a longitudinal direction from an upstream end of the conveyor to a downstream end of the conveyor. A motor drives the conveyor surface so that the conveyor surface defines a travel path that extends in the longitudinal direction. The conveyor surface sequentially receives and carries stringers toward the downstream end of the conveyor. An applicator mechanism is mounted above the conveyor surface and includes a reservoir containing coating material. The applicator mechanism further includes an actuator for providing a discharge mode and a retention mode. The discharge mode occurs while a stringer within the coating machine is in a predetermined position. A first volumetric flow rate of the coating material is discharged from the reservoir via a nozzle during the discharge mode. The nozzle directs the coating material to an applicator roller. The applicator roller applies the coating material to a stringer while the conveyor surface carries the stringer downstream along the travel path and past the predetermined position. The discharge mode is repeated for each of the stringers that are sequentially processed by the coating machine. The retention mode occurs while there is not a stringer in the predetermined position within the coating machine. Any volumetric flow rate of the coating material that is discharged from the reservoir during the retention mode is substantially less than the first volumetric flow rate.
In accordance with another aspect of the present invention, the applicator roller is movable toward and away from the conveyor surface, and the applicator roller is positioned closer to the conveyor surface during the discharge mode than during the retention mode.
In accordance with another aspect of the present invention, the motor drives the conveyor surface at a first speed during the discharge mode, and at a second speed that is slower than the first speed during the retention mode.
In accordance with another aspect of the present invention, a vacuum is drawn within the chamber of the applicator mechanism during the retention mode. The vacuum within the chamber restricts undesirable dripping of the coating material from the reservoir during the retention mode.
In accordance with another aspect of the present invention, at least one spreading mechanism is positioned downstream from the applicator roller for spreading the coating material applied to the stringer by the applicator mechanism.
In accordance with another aspect of the present invention, at least one alignment mechanism aligns the stringer with the applicator roller.
In accordance with another aspect of the present invention, at least one engagement mechanism forces the stringer against the conveyor surface.
The coating machine of the present invention reduces labor costs associated with aircraft construction by automatically applying coatings to the surfaces of stringers that are to abut the skin of an aircraft. The applied coatings are generally consistent from stringer to stringer and are generally uniform along the length of each stringer, even if the stringers have joggles or are of different sizes, which reduces aircraft corrosion.